This invention relates to a constant speed control device which controls a vehicle so as to run at a constant speed, and particularly to an apparatus which performs a control in accordance with steering angle information.
FIG. 3 shows the configuration of a conventional constant speed control device. In FIG. 3, the conventional device is provided with a vehicle speed sensor 1 for detecting a vehicle speed, an electronic control unit 2A for the constant speed control (hereinafter, referred to as "constant speed ECU"), a throttle actuator 3 which drives a throttle valve for controlling the intake air amount to an engine, a main switch 41 for starting the constant speed operation, a set switch 42 for setting conditions of the constant speed operation, a cancel switch 43 for canceling the constant speed operation, and a brake switch 44 for canceling similarly the constant speed operation. The conventional constant speed control device consists of these components.
FIG. 4 shows operation timings of signal wave forms, etc. of various portions of the conventional constant speed control device as described above.
The operation of the conventional device will be described with reference to FIGS. 3 and 4 as below. When the main switch 41 is turned on as shown in FIG. 4(c), the constant speed state is activated as shown in FIG. 4(b). The ECU 2A for the constant speed control sets the vehicle speed which is detected by the vehicle speed sensor 1 at the time of this ON operation, as the aimed vehicle speed V.sub.o as shown in FIG. 4(a). Then, the ECU 2A for the constant speed control controls the throttle actuator 3 so that the actual vehicle speed V.sub.r (see FIG. 4(a)) is adjusted within a predetermined range regarding the aimed vehicle speed V.sub.o.
When the cancel switch 43 or the brake switch 44 is turned on during the constant speed control as shown in FIG. 4(d), the ECU 2A for the constant speed control cancels the constant speed control. Thereafter, when the set switch 42 is turned ON as shown in FIG. 4(e), the ECU 2A for the constant speed control starts again the constant speed control.
In the case that an excessive load is applied to the engine (for example, the vehicle climbs a slope) during the above-mentioned constant speed control, even when the ECU 2A for the constant speed control drives the throttle actuator 3 at a maximum thereof so as to make the throttle valve open up, the actual vehicle speed V.sub.r may decrease to a lower level than the aimed vehicle speed V.sub.o, resulting in that the difference between these speeds exceeds V.sub.dif. In such a case, the ECU 2A for the constant speed control automatically cancels the constant speed control.
The conventional constant speed control device as described above has a problem in that, during when the constant speed operation is activated, there is possibility to perform the acceleration control even in the case that the deceleration must be done inherently corresponding to the running state of the vehicle, for example, when the vehicle is turning. Such an acceleration may frighten the driver, thereby causing the driver's drivingability to be impaired.